Downhole interpretation techniques using borehole dips

ABSTRACT

Embodiments of the disclosure involve a method comprising a method comprising inputting borehole dip data; determining characteristics of a plurality of dips based on the borehole dip data; applying one or more geological models to the characteristics; and generating one or more geological cross-sections based on geological modeling.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to and the benefit of European PatentApplication No. 16290032.8, titled “Downhole Interpretation TechniquesUsing Borehole DIPs,” filed Feb. 10, 2016, the entire disclosure ofwhich is hereby incorporated herein by reference and is a continuationin part of U.S. patent application Ser. No. 15/416,322, titled “DownholeInterpretation Techniques Using Borehole Dips” filed Jan. 27, 2017, theentire disclosure of which is hereby incorporated herein by reference.

BACKGROUND

The present disclosure relates to a method for interpreting a formationsurrounding a borehole, as well as systems and methods for analyzingformation geology using borehole dip data.

This section is intended to introduce the reader to various aspects ofart that may be related to various aspects of the present disclosure,which are described and/or claimed below. This discussion is believed tobe helpful in providing the reader with background information tofacilitate a better understanding of the various aspects of the presentdisclosure. Accordingly, it should be understood that these statementsare to be read in this light, and not as admissions.

Borehole image data may be utilized to evaluate the geometry and geologyof formation surrounding the borehole. The analysis of borehole imagedata may lead to a better understanding of geological structures in awellbore, including the identification of structural (e.g., bedding,faults, nonconformities, etc.) and sedimentary (e.g., cross-beddingbasal conglomerates, etc.) features. Distinguishing certain structuraland sedimentary features from non-structural geological events mayincrease the confidence and accuracy of formation interpretation andreservoir description.

SUMMARY

Embodiments of the disclosure involve a method for characterizinglaminations. The method involves inputting dips, which may be manuallycreated or obtained through semi-automatic dip picking, and computesstatistics and density of the lamination environment. The computedlamination environment data may be corrected for borehole deviation,such that they may be analyzed and compared regardless of boreholedeviation. As such, sequence recognition may be performed in singlewells or multiple wells. The present embodiments also involveidentifying and studying different scales of laminations and bedding,which may provide additional information for further interpretation.Embodiments may also include extracting information from particularlamination types based on their image properties. Embodiments mayfurther involve a lamination sequence recognition method, which mayinput such quantitative information and may be used for well-to-wellcorrelation, horizontal well correlation analysis, or geological trendanalysis.

Embodiments of the disclosure involve a method comprising a methodcomprising inputting borehole dip data; determining characteristics of aplurality of dips based on the borehole dip data; applying one or moregeological models to the characteristics; and generating one or moregeological cross-sections based on geological modeling.

The method further may include pre-processing the borehole dip datausing filtering, smoothing, calibrating, or combinations thereof. Themethod may further include removing perturbed dips inconsistent with aregional geological structure. The method may further include analyzingthe borehole dip data to determine a zone, model, polarity, orcombinations thereof, of the plurality of dips. The method may furtherinclude computing the lamination properties comprises classifyinglamination according to thick laminations or thin laminations.

In some embodiments, applying one or more geological models comprisesapplying a web model utilizing bisectors of perpendicular lines drawnbetween two adjacent dips of the plurality of dips. In some embodimentsapplying the web model comprises determining a plurality of bisectorthreads, each bisector thread of the plurality of bisector threads beinga bisector of a perpendicular of two adjacent dips; placing eachbisector thread between its respective two adjacent dips; identifying anintersection of the plurality of bisector threads, wherein theintersection is a point closest to a wellbore trajectory; determining anew iteration of a plurality threads including an intersection threadfrom the intersection; and iteratively determining a new iteration ofthe plurality of threads until there is no more intersection of thethreads. The method may further include creating a hinge zone based onthe iterative threads. The method may further include extending inputdips from the borehole dip data into the hinge zone. The method mayfurther include generating a cross-section based on the extension ofinput dips.

The disclosure also relates a method comprising inputting borehole data,determining characteristics of a plurality of dips and of at least afault based on the borehole data, applying one or more geological modelsto the characteristics, and generating one or more geologicalcross-sections based on geological modeling. Such a model may takefaults into account. In embodiments, the characteristics of the faultsmay include throws and type of faults.

The disclosure also relates a method comprising inputting borehole data,determining characteristics of a plurality of features based on theborehole data, wherein the plurality of features includes one or more ofa plurality of dips and a least one fault, applying a plurality ofhypothetical geological models to the characteristics, each hypotheticalgeological model having a specific combination of parameters, generatinga set of one or more geological cross-sections based on each of thehypothetical geological models, computing a correlation indicatorbetween each of the sets of cross-sections and values of at least oneborehole measurement. Based on the correlation indicator obtained foreach set, the method includes selecting a model among the hypotheticalmodels, and outputting the set of one or more geological cross-sectionsobtained with the selected model. Such a method enables to automaticallyoutput a model having the parameters that are best corresponding withthe borehole measurements obtained from the formation.

The disclosure also relates to a system comprising a downhole loggingtool and a processor that is configured to receive borehole datagenerated by the downhole logging tool, determine characteristics of aplurality of dips and of at least a fault based on the borehole data,apply one or more geological models to the characteristics, and generateone or more geological cross-sections based on geological modeling. Theprocessor of the system may be configured for performing all of theoperations of the methods described hereinabove.

The disclosure also relates to a computer-readable storage mediumcomprising program instructions for performing one or more of themethods according to the embodiments of the disclosure.

In accordance with the present disclosure, combinations of any of thesefeatures are considered.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a system for determining downholeparameters comprising a downhole tool positioned in a wellbore, inaccordance with embodiments of this disclosure.

FIG. 2 is a workflow for structural analysis of formation using boreholedip data, in accordance with embodiments of this disclosure.

FIG. 3 is an example of structure type matrix, in accordance withembodiments of this disclosure.

FIGS. 4A, 4B and 4C are schematic drawings representing computationalsteps of a parallel model, in accordance with embodiments of thisdisclosure.

FIGS. 5A and 5B are schematic drawings representing respectively thegeometry of a similar fold and a parallel fold, in accordance withembodiments of this disclosure.

FIGS. 6A to 6J are schematic drawings representing computational stepsof a web model, in accordance with embodiments of this disclosure.

FIGS. 7A to 7H are drawings representing the web model applied to awell, in accordance with embodiments of this disclosure.

FIG. 8 is a schematic drawing representing the relationship between axeson the stereonet in the web model, in accordance with embodiments ofthis disclosure.

FIG. 9 are graphical models showing a near-well three-dimensionalstructure model and a contour map of the top layer of the model, inaccordance with embodiments of this disclosure.

FIG. 10 are graphical models showing a three-dimensional surface modelscomparing when the transversal component of dips are taken into accountand when the transversal component of dips are not taken into account,in accordance with embodiments of this disclosure.

FIG. 11A is a schematic drawing a of web parallel model when theformation includes faults, in accordance with embodiments of thisdisclosure,

FIG. 11B is a result of the web model of FIG. 11A, in accordance withembodiments of this disclosure,

FIG. 12A is a schematic drawing of a web similar model when theformation includes faults, in accordance with embodiments of thisdisclosure,

FIG. 12B is a result of the web model of FIG. 12A, in accordance withembodiments of this disclosure,

FIG. 13 is a is a schematic drawing a of web parallel model and resultof the web model with dragging effect taken into account

FIG. 14 is a drawing of a web model when the formation includes faultswith a non-zero throw, in accordance with embodiments of thisdisclosure,

FIG. 15 is a drawing of cross-sections in the formation and a log of aparameter of a borehole, showing correlation between the log and thecross-sections.

DETAILED DESCRIPTION

One or more specific embodiments of the present disclosure will bedescribed below. These described embodiments are just examples of thepresently disclosed techniques. Additionally, in an effort to provide aconcise description of these embodiments, features of an actualimplementation may not be described in the specification. It should beappreciated that in the development of any such actual implementation,as in any engineering or design project, numerousimplementation-specific decisions may be made to achieve the developers'specific goals, such as compliance with system-related andbusiness-related constraints, which may vary from one implementation toanother. Moreover, it should be appreciated that such a developmenteffort might be complex and time consuming, but would still be a routineundertaking of design, fabrication, and manufacture for those ofordinary skill having the benefit of this disclosure.

When introducing elements of various embodiments of the presentdisclosure, the articles “a,” “an,” and “the” are intended to mean thatthere are one or more of the elements. The terms “comprising,”“including,” and “having” are intended to be inclusive and mean thatthere may be additional elements other than the listed elements.Additionally, it should be understood that references to “oneembodiment” or “an embodiment” of the present disclosure are notintended to be interpreted as excluding the existence of additionalembodiments that also incorporate the recited features.

Structural analysis of borehole image data may be used to creategeological cross-sections of formation surrounding a borehole. Sometechniques to better understand the geometry of geological structuresaround a well include complementing a structural description fromseismic data, but such data may be costly to acquire, and good qualityseismic data may be difficult when layer boundaries dip steeply (e.g.,at the limb of folds or around salt bodies). Near-well structuralinterpretation can also be initiated using only borehole dips of asingle well, but such interpretation may involve considerable expertiseas well as knowledge of the local geology. Manually drawing geologicalcross-sections may also be time consuming. Additionally, techniques forconstructing cross-sections with parallel layers may be suitable forregional and basin scale, but may not be sufficiently robust with realdata.

The present techniques involve one or more embodiments of a web modelworkflow for analyzing borehole dip data to generate a cross-sectionrepresentative of the formation. In some embodiments, the workflow mayresult in the instantaneous generation of geological cross-sections, aswell as the combination of cross-sections and/or dip data from multiplewells for an expansive model of geological structures over formationaround one or more wells.

In accordance with the present techniques, structural features, such asbedding, faults, and nonconformities, etc., and sedimentary featuressuch as cross-bedding and basal conglomerates, etc., may be recognizedand distinguished from non-structural geological events. Theidentification of structural and sedimentary features and distinguishingof these features from non-structural events may improve the confidenceand accuracy of interpretation and reservoir description. Accuratenear-well structural analysis may be used to analyze parallel layers,especially those with folds creating oil traps. The workflow of thepresent techniques may also make near-well structural analysis moreaccessible while shortening process times. Furthermore, structuralanalyses may also be more accurate and more automated when embodimentsof the present techniques are used in combination with other techniquessuch as automated dip detection and classification.

FIG. 1 is a schematic view of a wellsite 100 having an oil rig 102 witha downhole tool 104 suspended into a wellbore 106. A drilling mud,and/or a wellbore fluid 108, may have been pumped into the wellbore 106and may line a wall thereof. As shown, a casing 110 has also beenpositioned in the wellbore 106 and cemented into place therein. Thedownhole tool 104 may include one or more sensors for determining one ormore downhole parameters, such as wellbore fluid parameters and/orformation parameters. The wellbore fluid parameters, or properties, maybe determined by the one or more sensors independent of a determinationof the formation parameters.

The downhole tool 104 is shown as a wireline logging tool lowered intothe wellbore 106 to take various measurements. The downhole tool 104 mayinclude a conventional logging device 112, a sensor 116, one or moretelemetry devices 118, and an electronics package 120. The conventionallogging device 112 may be provided with various sensors, measurementdevices, communication devices, sampling devices and/or other devicesfor performing wellbore operations. For example, as the downhole tool104 is lowered, it may use devices, such as resistivity or other loggingdevices, to measure formation parameters and/or properties.

As shown, the downhole tool 104 may be conveyed into the wellbore 106 ona wireline 122. Although the downhole tool 104 is shown as beingconveyed into the wellbore 106 on a wireline 122, it should beappreciated that the downhole tool 104 may be a wireline tool, ameasurement-while-drilling tool, a logging-while-drilling tool, or anysuitable tool, conveyed through any suitable conveyance, such as a slickline, a coiled tubing, a drill string, a casing string and the like. Thedownhole tool 104 may be operatively connected to a surface unit 114 forcommunication between these units. The downhole tool 104 may be wiredvia the wireline 122, as shown, and/or wirelessly linked via the one ormore telemetry devices 118. The one or more telemetry devices 118 mayinclude any telemetry devices, such as electromagnetic devices, forpassing signals to a surface unit 114 as indicated by communicationlinks 124. Further, it should be appreciated that any communicationdevice or system may be used to communicate between the downhole tool104 and the surface unit 114. Signals may be passed between the downholetool 104 and the surface unit 114 and/or other locations forcommunication between these units.

While the downhole tool 104 is depicted as the wireline tool 104 havingthe sensor 116 thereon, it will be appreciated that the sensor 116 maybe positioned downhole on a variety of one or more tools. For example,the sensor 116 may be placed downhole on a drillstring, coiled tubing,drill stem tester, production, casing, pipe, or other downhole tool.Although only one sensor 116 is shown, it should be appreciated that oneor more sensors 116 and/or portions of the sensors 116 may be located atseveral locations in the wellbore 106. The sensor 116 is preferablypositioned about an outer surface of the downhole tool 104 so that thedownhole fluid may pass along for measurement thereof. However, it willbe appreciated that the one or more sensors 116 may be positioned atvarious locations about the wellsite 100 as desired for performing fluidmeasurement.

The electronics package 120 may include any components and/or devicessuitable for operating, monitoring, powering, calculating, calibrating,and analyzing components of the downhole tool 104. Thus, the electronicspackage 120 may include a power source, a processor, a storage device, asignal conversion (digitizer, mixer, amplifier, etc.), a signalswitching device (switch, multiplexer, etc.), a receiver device and/or atransmission device, and the like. The electronics package 120 may beoperatively coupled to the sensor 116. The power source in theelectronics package 120 may apply a voltage to the sensor 116. The powersource may be provided by a battery power supply or other conventionalmeans of providing power. In some cases, the power source may be anexisting power source used in the downhole tool 104. The power sourcemay be positioned, for example, in the downhole tool 104 and wired tothe sensor 116 for providing power thereto as shown. Optionally, thepower source may be provided for use with the sensor 116 and/or otherdownhole devices. Although the electronics package 120 is shown as oneseparate unit from the sensor 116, it should be appreciated that anyportion of the electronics package 120 may be included within the sensor116. Further, the components of the electronics package 120 may belocated at various locations about the downhole tool 104, the surfaceunit 114 and/or the wellsite 100. The sensor 116 may also be wired orwirelessly connected to any of the features of the downhole tool 104,and/or surface unit 114, such as communication links, processors, powersources or other features thereof.

The sensor 116 may be capable of determining one or more downhole fluidparameters and/or one or more formation parameters. The downhole fluidsmay include any downhole fluids such as downhole mud (e.g., oil based),hydrocarbons, water and/or other downhole fluids. The sensor 116 maydetermine the downhole parameters of the downhole fluids and/or thedownhole formations as the downhole tool 104 passes through the wellbore106. Due to the harsh conditions of the downhole environment, the sensor116 may be positioned on the downhole tool 104 in such a manner that thesensor 116 is capable of measuring fluids as the downhole tool 104passes through the wellbore 106. Further, the sensor 116 may bepositioned in such a manner that reduces clogging of downhole fluids asthe downhole fluids pass the sensor 116. As shown, the sensor 116 ispositioned on an outer surface 126 of the downhole tool 104. The sensor116 may also be positioned at various angles and locations.

Formation properties measured by the downhole tool 104 may be processedinto a borehole image. For example, portions of such processing mayoccur at the downhole tool 104, the surface unit 114, or at any othersuitable processor. The borehole image may be received from a downholetool 104 having any type of conveyance, and having any type of sensorgeometry or arrangement, including both pad-based and rotating sensors,and input dips. For example, borehole images, as well as other images(e.g., core images) or other types of suitable data (e.g., highresolution 1D data), may be used.

FIG. 2 is a workflow for using borehole dip data to generate geologicalcross-sections of a formation near a borehole, in accordance with one ormore embodiments of the present techniques. The workflow involves usingborehole dip data from formation surrounding and along a boreholetrajectory, which may include bed boundary dip obtained in any suitableway, including manual delineation or automated dip detection fromformation image data obtained from any suitable tool, such as from tool104. Additionally, in some embodiments, other information may also beused in the workflow, such as faults, nonconformities, or otherstructural features. In some embodiments, the dip data may bepre-processed, including filtering, smoothing, calibrating, etc.,resulting in processed dips. For example, filtering the dip data mayremove perturbed dips which may not be consistent with the regionalgeological structure, such that the remaining dips are more consistentwith structural dips at the regional scale. Further, structural dips maybe extracted from the sedimentary structure using other suitablemethods. A

The workflow may also involve automatic and/or interactive structureanalysis of the dips, including analysis of the zone, model, and/orpolarity of the dips. The automatic and/or interactive structuralanalysis may involve refining zones of the same structural unit alongthe well trajectory. A structural unit may include a set of layersaffected by a common deformation and/or tilting. Without a prioriknowledge, the number of structural units penetrated by the well may notbe known. In some embodiments, a zone may be identified based on thepattern of poles on the stereonet. There may be two patterns based onthe geological principles. A first pattern may include a concentrateddistribution observed when the structure is not deformed (e.g.,monocline) and may be characterized by the mean dip and also the strikeof the mean dip (e.g., the pseudo-structural axis). A second pattern mayinclude an elongated distribution along a great circle (e.g., acylindrical structure) or a small circle (e.g., a conical structure),and may be observed when the structure is deformed (e.g., by folds,faults with drags). The second pattern may be characterized by thestructural axis which corresponds to the pole of the plane of the greator small circle and also conicity, if distributed along a conicalstructure.

In some embodiments, an automatic zonation method may be used, wheredips may be differentiated according to the different patterns. Anautomatic zonation method may involve grouping consecutive dips withthresholds and combining the groups if they are considered to belong tothe same structure unit after checking the pattern of dips on thestereonet. The zones may then be verified and refined by analyzing dipson several plotting tools and by using all the available external data,such as faults and nonconformities observed on the borehole image andlithological logs (e.g., gamma rays). The stratigraphic polarity foreach dip may be defined to be normal or reverse, and possible geologicalstructures may be estimated based on the structural type.

In some situations, defining zones may be affected by the scale of thestructure. For example, a monocline structure at a small scale may bepart of the limb of a fold at a larger scale. Some embodiments involvevisualizing the structure type as a function of the scale, as providedin FIG. 3, which is an example of a structure type matrix. The x-axis ofthe graph of FIG. 3 is the length of the scale, and the y-axis is themeasured depth. The shaded region to the right represents the secondpattern, and the shaded region to the left represents the first pattern.The matrix may be generated by testing for the second pattern with thedips in a sliding window along the measured depth. If the second patternis not detected, the program may test the dips for the first pattern.The color density shows the quality of a fit represented by the fittingerror. In some embodiments, a summary log may be created to representthe structure along the measured depth.

Once the structural zones are set, the workflow involves applying one ormore geological models on the structural zones (and/or models, polarity)to construct geological cross-sections. In some embodiments, smoothingmay be applied to further eliminate erratic dips. Further, in someembodiments, a resampling may be applied when structural dips are poorlysampled. Several geological scenarios may be analyzed by applyingdifferent models and modifying the structural zones. In someembodiments, the computed cross-section may be validated, and thedisplay of the structure may be highlighted with a lithology log. Insome embodiments, further data, such as sedimentary dips may also beused in the construction of geological cross-sections.

Different types of geological models may be used to construct thegeological cross-sections. For example, two conventional geometricmodels involve constructing geological layers and respecting differentassumptions in the geometry of the layers. The geometric models, thesimilar model and the parallel model, may assume similarity andparallelism, respectively, in the geometry of the layers. Both modelsmay build layer geometries by translating dips in the direction along aspecific two-dimensional plane (e.g., the translation plane). In thesimilar model, the translation plane may be common to all the dips,while in the parallel model, the translation plane may be unique to eachdip and defined as a plane orthogonal to the dip plane.

The computation steps of the parallel model is represented in theschematic diagram of FIG. 4. In FIG. 4a , dips and translation planesare projected on a two dimensional plane, where dips are represented bythe solid lines, and the translation plane is represented by the dottedtranslation axis. Layer lines are then created using only the angles ofthe dip lines. A layer line at the nth dip may be successively extendedby translating dip lines one after another in the respective directionsof their translation axis, and then linked at the intersection. Theposition of the translated dip line is constrained by the previousneighboring dip line. In other words, the translated line and theprevious line is at the same distance from the intersection of theirextended lines, as shown in FIG. 4b . The computed layer line for thenth dip is a polyline (i.e., continuous line composed of line segments,made with intersections of the extended lines of the nth dip and the N−1translated dips, where N is the number of input dips. FIG. 4c shows thegeometry of layers computed for the first, second, and fourth dips fromthe top.

Using a common translation plane for all the dips results in layershaving the same thickness in the direction of the translation axis andidentical geometries in the layers. This corresponds to the definitionof the geometry of similar fold. The layer thickness of the similar foldmay be constant in the direction of the axial plane, as shown in FIG. 5a. In the similar fold model, the translation plane is selected so thatit corresponds to the axial plane, which goes through the middle of theelongated cloud of poles on the stereonet. The method may be applicableto faults with drags, rollover and monocline structures, assuming theyare similar structures or part of a similar structure. The translationplanes may be defined as the fault plane, the detachment plane, and theplane containing the pole of the mean dip, respectively. On the otherhand, the parallel model preserves the layer thickness measuredperpendicularly to the initial dips, which corresponds to the layerthickness before folding, as shown in FIG. 5b . This corresponds to thedefinition of the parallel fold. The instability of the parallel modelmay be due to the translation axes crossing each other inside the hingezone of folds.

In one or more embodiments of the present techniques, a workflow forusing borehole dip data to create geological cross-sections may involveusing a web model for modeling the cross-sections. The web model mayinvolve the creation of radials (e.g., warp threads) and methodicallymaking a spiral (e.g., weft thread) using the radials as guide lines.The web may not be made of concentric circles, but may instead be aspiral. The geometry of the web may be similar to that of a concentricfold whose layer thickness is parallel.

The web method may also include two steps. A first step of the webmethod may be to construct warm threads (e.g., the guiding web) and dippropagation using the warp threads. The cross section may be created ona two-dimensional plane where the true thickness is preserved andrepresents the structure. In instances where the dips follow the secondpattern, the plane perpendicular to the structural axis may be the planeon which the structural cross section must be constructed. In instanceswhere the dips follow the first pattern, the plane perpendicular to thepseudo-structural axis may be used. The stratigraphic polarity of dipsmay also be taken into account.

FIG. 6 is a schematic drawing representing the computational steps ofthe web model in accordance with the present techniques. A guiding webmay be created from the dips on the well trajectory, as shown in FIG. 6a. The threads drawn in FIG. 6b represent the bisectors of perpendicularsof adjacent dips placed between the two adjacent dips. In someembodiments, the input data may be maximized by adding theperpendiculars of the top and bottom dips, so that the number of initialthreads corresponds to the number of initial dips plus one.

The bisector threads of FIG. 6b may be extended, and an intersection ofbisector threads closest to the well trajectory may be identified, asrepresented in FIG. 6c . The bisector threads may be stopped at theintersection (e.g., of Tn and Tn+1), and continued with a new thread, asshown in FIG. 6d . The set of threads may be updated by removing thebisector lines of the intersection (e.g., Tn and Tn+1) and adding a newthread from the intersection (e.g., Tnew). The direction of the newthread may be defined as the bisector of the perpendicular to the dipsjust above Tn and just below Tn+1. As shown in FIGS. 6e and 6f , theidentification of a new intersection and a continuation of a new threadfrom the intersection may be iteratively performed, extending the guideline along the intersections. The iteration may end when no moreintersection is found, or if there is only one thread in the set, asshown in FIG. 6g . The warp threads delineates the two-dimensional planeinto several areas, with each area containing one dip.

The second portion of the web model is the creation of the cross-sectionby extending the input dips. The input dips may be extended to reach thelimit of their area, where the lines continue but use the dip angle ofthe next area, as shown in FIG. 6h . FIG. 6i shows additional extensionof input dips for more of the dips along the trajectory, and FIG. 6jshows a portion of the resulting cross-section. The outside of the hingezone shows the same geometry as in the parallel model, but in the webmodel, the inside of the hinge zone is also reconstructed due to themerged guiding threads. As such, the web model may be effective forconstructing parallel layers including a parallel fold in a verticalwell and a monocline structure in a horizontal well. The method may notwork when the input dips are nearly perpendicular to the welltrajectory, because the guiding web becomes very narrow and dips cannotbe propagated away from the well. The gradual change of dips may lead toa smoother geometry at the hinge zone of the fold.

The web model may also take into account faults, as shown inrelationship with FIG. 11. The web model is the same as previouslyexplained (parallel model), except that, in the first portion of the webmodel, the threads drawn in relationship with a fault are labeleddifferently than the ones drawn in relationship with a dip. To bettervisualize it FIG. 11A shows a well trajectory 200 with dips 202 andfaults 204 as well as guiding grid 206. The threads 208 of the guidinggrid are drawn as explained before when related to dips and aredesignated as “dip threads” in the following. In this particularembodiment, they represent the bisectors of perpendiculars of adjacentdips placed between the two adjacent dips and may also be designated as“bisector threads”. However, when there is a fault, the thread 210relative to this fault—designated as “fault thread” in the following—isplaced at the fault position and has the same angle than the faultangle. In this case, there is no dip thread drawn between two adjacentdips when a fault is interposed between the adjacent dips. For instance,there is no thread between adjacent dips 202 a-202 b. Further, when anintersection is identified between a fault thread and a dip thread suchas intersection 212, the threads are merged and follow the fault thread.When an intersection 214 between two fault threads is identified, thethreads merge and follow one of the fault thread, for instance manuallyor automatically prioritized in view of other indications or parametersobtained relative to the borehole and/or the formation. FIG. 11B showsthe results of a web model using a parallel fold when faults 204 havebeen detected on the well trajectory.

The faults may also be taken into account in a similar fold as shown onFIG. 12. In this case, represented on FIG. 12A, wherein the dips 202 andfaults 204 are the same as on FIG. 11A, the dip threads 216 are drawnparallel to each other and to a predetermined axis and are designated as“collateral threads”, and the fault threads 210 are the same as the onesof FIG. 11A, ie placed at the fault position and with the same anglethan the fault angle. As explained in relationship with FIG. 12A, whenan intersection is identified between a fault thread and a dip threadsuch as intersection 218, the threads are merged and follow the faultthread 210 and when two faults interception, such as in 220, the threadsmerge and follow one of the fault thread. FIG. 12B shows the results ofa web model using a similar fold when faults 204 have been detected onthe well trajectory.

In another embodiment, the dip threads situated near to a fault threadmay be set as parallel to the fault thread. In this case, the high angledips, due to a dragging effect, can be highlighted in the finalstructure. The threshold distance from dip thread to fault thread underwhich such rule is applied may be determined manually or automatically.

FIG. 13 shows the result of a parallel web model when dragging effecthas been taken into account. On FIG. 13, dip threads 222 and faultthreads 224 are shown. The dip thread are bisector threads 225, exceptfor the dip threads 226 immediately adjacent from the fault, which aredrawn parallel to the adjacent fault thread (designated “drag threads”).The results then show a different structure, accounting for the draggingeffect. When it is believed that dragging effect is important, it ispossible that more than one adjacent dip threads are considered asparallel to the fault threads (for instance the two adjacent dip threadson each side of the fault thread). The drag threads can be defined bythe distance (measured depth or offset distance) from the fault, and thedistance can be determined based on the variation of the dip byinterpreter or an automatic method.

In the example of FIG. 13, the drag threads have been described as partas the parallel web model. However, drag threads may also be presentwhen the model is a similar model and the other dip threads arecollateral dip threads. Furthermore, in the example of FIG. 13 eachfault generates dragging effect. However, when several faults have beendetermined as part of the formation, one portion of the faults might beassociated with dragging effect while the other portion is not.Therefore, the dip threads adjacent to one predetermined fault may bedrag thread while dip threads adjacent to another predetermined faultare collateral or bisector threads, depending on the model type.

In a particular embodiment, the web model, whether it uses a similar ora parallel fold, may also take into account further attributes of aparticular fault. In a particular embodiment of the model, theattributes may be the throw of the fault and the type of the fault(normal fault or reverse fault). A fault throw is a vertical componentof the displacement of the block of geological formation along thefault. A normal fault is a geological fault in which the rock above thefault plane has moved downward relative to the rock below the faultplane while a reverse fault is a geological fault in which the rockabove the fault plane has moved upward relative to the rock below thefault plane. The web model taking into account a throw of the faultcomprises specific operations in the second portion of the model. Theoperations include, first, the computation of the magnitude of thedisplacement based on the throw. It is a simple computation as follows:D=T×sin(θ)

-   -   wherein D is the displacement along the fault thread, T the        throw, and θ the angle of the fault thread relative to the        horizontal axis (axis perpendicular to the Z axis).

While extending the input dips, when a dip line (first dip line)intersect a thread at the limit of an area, as previously explained, thedip line is extended in a second adjacent area by a second dip lineusing the dip angle contained in the second area. When the first dipline intersects a fault thread at the limit of an area, the web modelmay include shifting the position of the intersection of the faultthread with the second dip line over the distance D along the faultthread in the direction indicated by the type of the fault. In otherwords, the dip lines in two adjacent areas delimited from each other bya dip thread intersect at the dip thread while the dip lines of twoadjacent areas delimited by a fault thread having a non-zero throw donot intersect. Further, their intersecting points with the fault threadare separated by the distance D. As the fault throw is taken intoaccount, when forming the guiding web (first portion of the model), thefault threads are merging into one resulting fault thread (as indicatedabove) from the intersection of both fault threads and the sum of thethrows of both of the fault threads is assigned to the resulting faultthread. The mathematical sign of the throw may be chosen in function ofthe direction of the displacement.

FIG. 14 shows the results of the web model when faults including onefault with non-zero throw have been detected in the well trajectory. Inthis case, three faults 230, 232, 234 have been detected. Faults 230 and232 intersect at location 236, forming fault 237, and fault 232 and 234intersect at location 238, forming fault 239. Fault 232 has a throw of3. Therefore, it can be seen that the dip lines are shifted of adistance D when the dip lines cross the fault 232. For instance, it isvisible that the dip line 240 representing the lowermost limit of thelayer structure is extended in another area separated from the first bythe fault 232 (having a non-zero throw) by dip line 242. The dip lines240 and 242 do not intersect at fault 232 and their respectiveintersection with fault 230 are distant from D. At the location 236,when the fault threads 230 and 232 are merging and the throw ispropagated to the merged fault thread 237 (and then 239) so that the diplines are also shifted when they cross the merged fault threads.

Some or all of the parameters of the model such as the following:

-   -   type of fold (parallel or similar), ie type of dip threads        (bisector threads or collateral threads). The translation axis        for the similar model may also be considered as a parameter of        the model.    -   dip amplitudes and azimuths (variations are possible around the        measured values due to measurement's incertainties),        -   throw or type of faults (if any)        -   existence and extent of a dragging effect,    -   When faults intersect, the fault that is prioritized may also be        considered as a parameter of the model.    -   may be selected by an user in view of borehole measurements.        However, these parameters are not always easy to estimate in        view of borehole measurements, depending on the well trajectory        and how it intersects the formation. In an embodiment of the        disclosure, it is proposed to automatically estimate such        parameters. The estimation is performed by creating a set of        hypothetical models, each hypothetical model being a different        combination of possible values of each of the parameter, the set        of hypothetical models covering all of the possible combinations        of values for the parameters. For each hypothetical model, the        model indicates that the well trajectory intersects each layer i        one or several times (the number of times is defined as J(i)) at        predefined depth intervals. It can be mathematically expressed        as follows:        Interval(i,j)=[z _(startj) ^(i) ,z _(endj) ^(i)] for i=1 . . .        N,j=1 . . . J(i)    -   wherein i is the identifier of a given layer, Interval (i, j)        are the depth intervals at which the well trajectory crosses        said layer i, z_(startj) ^(i) and z_(endj) ^(i) are the start        and stop depths of the j^(th) interval where the well trajectory        crosses the layer.

When each layer in each model has been characterized as mentioned above,the correlation between log values, corresponding to boreholemeasurements as a function of depth, on all the intervals correspondingto the same layer i is computed. For instance, x being a log value, thefollowing calculation is performed:

Correlation(i) = corr(x[z_(start 1)^(i), z_(end 1)^(i)], …  , x[z_(startJ(i))^(i), z_(endJ(i))^(i)])${Correlation} = {\frac{1}{N}{\sum\limits_{i = {1\ldots\; N}}{{Correlation}(i)}}}$

When several borehole measurements are obtained, it is possible tocalculate the correlation for each of the corresponding log values inthe same manner. The term Correlation(i) may therefore be the mean orweighted mean of the correlations for the different measurements.Moreover, in the embodiment above, the correlation is taken as the meanof the correlation over all the pairs, but it could be defineddifferently (median or weighted mean, for instance). When the intervalsare not of the same length, the method rescales the log values with aproper interpolation in order to make the lengths the same to computecorrelation. In view of the correlation values for each of thehypothetical models, the probability for each of the parameters may becomputed. Monte Carlo outputs for instance a probability map for eachhypothetical model. Extracting maxima enables to propose multipleprobable scenario to users.

FIG. 15 shows for instance a trajectory of the well in a formation (onthe left), and the log of borehole measurement associated (on theright). In view of the correlation between the different log values, itis possible to identify the limits between each of the layers and theparameters of the fault.

FIG. 7 shows photos, stereonets, and portions of geologicalcross-sections obtained using the workflow and web model of the presenttechniques. The geological structure in FIG. 7 was folded withanticlines and synclines of different wavelengths and layer thicknesses.The dips show a second pattern on the stereonet, where the middle partis an anticline fold with smaller curvature than the rest. The rightside of the structure extends relatively horizontally. Well V wasdrilled vertically from the right side of the limb, and well H wasdrilled horizontally through the fold axes. Geological cross-sectionswere created for both vertical and horizontal wells, as shown in FIGS.7e and 7h , respectively. As can be seen in FIG. 7e , the dips arepropagated sufficiently to the left side because the angle between theperpendicular of the bottom dip and the well is relatively large, whilethe right side is not because the corresponding angle of the top dip issmall. In well H, a relatively large volume of the structure can bereconstructed.

In some embodiments, the cross-section may be computed on a planeperpendicular to the structural axis (e.g., the second pattern) of thepseudo-structural axis (e.g., the first pattern). Assuming that thestructure is continuous in the direction perpendicular to thecross-sectional plane, the three-dimensional model may be created bytranslating the nodes composing the layer lines on the two-dimensionalcross-section along an axis (e.g., the translation axis). Thetranslation axis of a cylindrical structure and a monocline structurecorrespond to the structural axis and the pseudo-structural axis,respectively, and they may be common to all the nodes. For conicalstructures, the translation axis deviates relative to the structuralaxis by an angle that is equal to the difference between 90 degrees andthe degree of conicity. Based on this angle, the orientation of thetangent line may be computed by rotating the pole around the structuralaxis by approximately 90 degrees, as shown in FIG. 8. FIG. 8 includesschematic representation of the axes on the stereonet, dipping 10degrees in aximuth 305 degrees, where the conicity of the small circleis 75 degrees. The translation axis may correspond to the outer productof the pole and the tangent line. In some embodiments, the method may begeneralized for cylindrical structures whose conicity is approximately90 degrees. Additionally, in some embodiments, the transversal componentof dips (e.g, apparent dip inclination in the azimuth of structuralaxis) may be taken into account, as represented in FIG. 10b . In theseinstances, the translation axis may be smoothed taking into account thelength of segment (i.e., smaller weight on smaller segments) and theoverall effect of transversal component may be adjusted (e.g., from 0,no effect, to 1, full effect).

FIG. 9 shows the near-well three-dimensional model of the structurecomputed in the well H of FIG. 7, as well as its map view. The well maybe assumed to be in the direction of the azimuth of approximately 40degrees. The structural axis may be perpendicular to the computedcross-section (i.e., dipping an angle of approximately 20 degreestowards a 310 degree azimuth). The offset of projection may be set(e.g., to approximately 50 meters).

To display a cross-section on a given plane, and not onlyperpendicularly to the structural axis, the intersections of thethree-dimensional surfaces and the plane may be computed. Thecross-section may be a vertical section containing the well trajectory,and may be approximated by a set of vertical planes. The computedcross-section may also be projected on the curtain section by searchingthe intersections between the three-dimensional surfaces and thevertical planes. Alternatively, in some embodiments, thethree-dimensional model may be created from multiple cross-sectionscreated on several planes with varying angles. The cross-sections may beused in a three-dimensional space, and all the layers nodes form a givenlayer boundary may be recognized and connected.

Plural instances may be provided for components, operations orstructures described herein as a single instance. In general, structuresand functionality presented as separate components in the exemplaryconfigurations may be implemented as a combined structure or component.Similarly, structures and functionality presented as a single componentmay be implemented as separate components. These and other variations,modifications, additions, and improvements may fall within the scope ofthe inventive subject matter.

What is claimed is:
 1. A method comprising: inputting borehole dataobtained by measuring downhole one or more local properties of aborehole crossing a geological formation with a downhole logging tool;determining characteristics of a plurality of dips and of at least afault based on the borehole data, wherein the characteristics each ofthe plurality of dips and of the at least one fault include position andangle; applying one or more geological models to the characteristics;wherein applying one or more geological models comprises applying a webmodel utilizing fault threads drawn at position and angle of thecharacterized fault and generating one or more geological cross-sectionsrepresentative of the geological formation in the vicinity of theborehole based on geological modeling.
 2. The method of claim 1, furthercomprising pre-processing the borehole data using filtering, smoothing,calibrating, or combinations thereof.
 3. The method of claim 1, whereinapplying one or more geological models additionally comprises applying aweb model utilizing dip threads drawn between two adjacent dips of theplurality of characterized dips.
 4. The method of claim 3, wherein thedip threads correspond to one or more of: bisector threads, defined asbisectors of perpendicular lines drawn between two adjacent dips of theplurality of characterized dips, collateral threads, defined asparallels to a predetermined translation axis, drag threads, defined asparallel to an adjacent fault thread.
 5. The method of claim 1, whereinapplying the web model comprises: determining one or more fault threads,and placing each fault thread at a fault position, determining aplurality of dip threads, placing each dip thread between its respectivetwo adjacent dips, at equal distance from each of the adjacent dips. 6.The method of claim 5, wherein applying the web model comprises:identifying an intersection of at least one of the dip threads with atleast one of the fault thread, merging the dip thread with the faultthread so that the dip thread follows the fault thread from theintersection.
 7. The method of claim 5, wherein applying the web modelcomprises, when a plurality of fault threads have been determined:identifying an intersection of at least two of the fault threads,determining a prioritized fault thread and a non-prioritized faultthread from the two intersecting fault threads, merging the faultthreads so that the non-prioritized fault threads follows theprioritized fault thread from the intersection.
 8. The method of claim5, wherein the dip threads correspond to bisector threads, defined asbisectors of perpendicular lines drawn between two adjacent dips of theplurality of characterized dips and wherein applying the web modelcomprises: identifying an intersection of the plurality of bisectorthreads and defining an intersection thread replacing the intersectingbisector threads from the intersection; determining a new iteration of aplurality of threads including the intersection thread; and iterativelydetermining a new iteration of the plurality of threads until there isno more intersection of the threads.
 9. The method of claim 1, whereincharacteristics of a fault thread include a fault throw and a type offault.
 10. The method of claim 9, wherein applying the web modelcomprises: determining a plurality of dip threads, and placing each dipthread between its respective two adjacent dips, at equal distance fromeach of the adjacent dips; determining a plurality of fault thread, andplacing each fault thread at a fault position, wherein each fault threadis associated to a fault throw, identifying an intersection of at leasttwo of the fault threads, determining a prioritized fault thread and anon-prioritized fault thread from the two intersecting fault threads,merging the fault threads so that the non-prioritized fault threadsfollows the prioritized fault thread from the intersection, applying tothe merged fault thread the sum of the fault throws associated to theintersecting fault threads.
 11. The method of claim 3, wherein the faultthreads or dip threads delimit areas and wherein generating one or moregeological cross-sections based on geological modeling includes forminga first dip line by extending a first input dip to reach the limits ofan area in which the input dip is situated, and extending the first dipline into an adjacent area with a second dip line, wherein the seconddip line follows the dip angle of a second input dip situated in theadjacent area.
 12. The method of claim 11, wherein the thread separatingtwo adjacent areas is a fault thread, wherein the fault thread ischaracterized by a throw and a type of fault, and wherein generating oneor more geological cross-sections based on geological modeling includes,at the fault thread, shifting an intersection point of the second dipline with the fault thread relative to an intersection point of thefirst dip line with the fault thread over a predetermined distance andin a predetermined direction along the fault thread, wherein thepredetermined distance is obtained as a function of the fault throw andthe predetermined direction is obtained as a function of a type of thefault.
 13. A method comprising: inputting borehole data obtained bymeasuring downhole one or more local properties of a borehole crossing ageological formation with a downhole logging tool; determiningcharacteristics of a plurality of features based on the borehole data,wherein the plurality of features includes one or more of a plurality ofdips and at least one fault and wherein the characteristics of each ofthe features include position and angle of the feature; applying aplurality of hypothetical geological models to the characteristics,wherein each hypothetical geological model is a web model utilizing dipthreads drawn between two adjacent dips of the plurality ofcharacterized dips and fault threads drawn at position and angle of thecharacterized fault, wherein each hypothetical geological model has aspecific combination of parameters relative to the geological formation;and generating a set of one or more geological cross-sections based oneach of the hypothetical geological models, computing a correlationindicator between each of the sets of cross-sections and values of atleast one of the measured borehole properties, based on the correlationindicator obtained for each set, selecting a model among thehypothetical models, outputting the set of one or more geologicalcross-sections representative of the geological formation in thevicinity of the borehole obtained with the selected model.
 14. Themethod of claim 13, wherein the parameters of each model include one ormore of the following: type of dip threads (collateral, drag or bisectorthreads); dip amplitudes and azimuths, if faults are determined from theborehole data, a throw and/or a type of fault for each of the fault. 15.A system, comprising: a downhole logging tool configured to be loweredin a borehole crossing a geological formation and to acquire boreholedata, wherein acquiring borehole data includes measuring one or morelocal properties of the borehole; a processor that is configured to:receive the borehole data generated by the downhole logging tool;determine characteristics of a plurality of dips and of at least a faultbased on the borehole data, wherein the characteristics each of theplurality of dips and of the at least one fault include position andangle; apply one or more geological models to the characteristics,wherein applying one or more geological models comprises applying a webmodel utilizing fault threads drawn at position and angle of thecharacterized fault; and generate one or more geological cross-sectionsrepresentative of the geological formation in the vicinity of theborehole based on geological modeling.
 16. The system of claim 15,wherein the processor is further configured to apply one or more webmodels utilizing dip threads drawn between two adjacent dips of theplurality of characterized dips.
 17. The system of claim 16, wherein thedip threads correspond to: bisector threads, defined as bisectors ofperpendicular lines drawn between two adjacent dips of the plurality ofcharacterized dips, collateral threads, defined as parallels to apredetermined translation axis, drag threads, defined as parallel to anadjacent fault thread.
 18. The system of claim 15, wherein the processoris further configured to: determine one or more fault threads, andplacing each fault thread at a fault position, determine a plurality ofdip threads, place each dip thread between its respective two adjacentdips, at equal distance from each of the adjacent dips; perform at leastone of the following operations: identify an intersection of at leastone of the dip thread with at least one of the fault thread, and mergethe dip thread with the fault thread so that the dip thread follows thefault thread from the intersection, and/or when a plurality of faultthreads have been determined, identify an intersection of at least twoof the fault threads, determine a prioritized fault thread and anon-prioritized fault thread from the two intersecting fault threads,and merge the fault threads so that the non-prioritized fault threadsfollows the prioritized fault thread from the intersection.
 19. Thesystem of claim 18, wherein characteristics of a fault thread include afault throw and a type of fault, and wherein the processor is furtherconfigured to apply to the merged fault thread the sum of the faultthrows associated to the intersecting fault threads.
 20. The system ofclaim 15, wherein the processor is further configured to: apply aplurality of hypothetical geological models to the characteristics, eachhypothetical geological model having a specific combination ofparameters; and generate a set of one or more geological cross-sectionsbased on each of the hypothetical geological models, compute acorrelation indicator between each of the sets of cross-sections andvalues of at least one borehole measurement, based on the correlationindicator obtained for each set, select a model among the hypotheticalmodels, output the set of one or more geological cross-sections obtainedwith the selected model.